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 "Mitochondrial Disease And Deafness"


By Colleen Powell

UMDF Youth Ambassador of Horsham Pennsylvania
 

 

Mitochondrial Disease And Deafness

 

            Genetic factors are thought to cause more than 50% of all incidents of congenital hearing loss in children. (Canalis and Lambert, 2000) Hearing loss that is congenital have three causes; autosomal dominant, autosomal recessive and X-linked hearing. Today I will be focusing on an autosomal dominant/autosomal recessive cause; Mitochondrial Disease.
 

            Mitochondria produce the energy our bodies need to sustain life. When these compartments fail they cause injury or complete failure of the organ affected. Mitochondria are very complex organelles located in virtually all cells of the body. Neither the mitochondria nor the cell can exist without the other. Interestingly, mitochondria have a separate set of genes that are not part of the cell's genes. Changes in the mitochondrial genes can also result in syndromes involving hearing loss. Hearing Loss and Deafness are symptoms of Mitochondrial Disease.


            Sensorineural hearing loss is the most common type of permanent hearing loss and the main cause of hearing impairments of those with mitochondrial diseases. Sensorineural hearing loss can be mild, moderate, or severe, including total deafness and is almost always permanent. Abnormalities in the hair cells in the cochlea are the main cause of Sensorineural Hear Loss Some patients may also have abnormalities in the central auditory system of the brain causing impairment.


            There are many defects of the Mitochondria that will cause hearing impairment. One of these is known as MERRF or myoclonic epilepsy and Ragged-Red Fiber Disease. MERRF is a progressive multi-system syndrome usually beginning in childhood, but onset may occur in adulthood. The rate of progression varies widely (UMDF, 2012)


            Another common cause is KSS or Kearns-Sayre Syndrome. KSS is a slowly progressive multi-system mitochondrial disease. The main symptoms include paralysis of the eye muscle, cardiac blocks, ataxia and deafness. KSS is a very rare disorder. One online eMedicine article found only 226 cases worldwide in the literature by 1992 Kearns-Sayre Syndrome by Ewa Posner,MD)


            Defects in the Mitochondrial Complexes are one also another cause of deafness. This is the case in mainly Complex I and Complex III disorders. These disorders are mainly autosomal recessive. Hearing loss is also accompanied by weakness, short stature, ataxia and dementia.


            When it comes to Deaf culture, we realize there is a dividing barrier between those who are deaf and hearing. That would be communication. Many patients affected by deafness due to mitochondrial disease never get the chance to take a part in Deaf Culture. Lack of muscle strength and developmental delays make it hard for most to learn sign language or other means of communication. Deafness due to mitochondrial disease happens most often at birth. The child never has the opportunity to learn so they basically have very little ability to communicate.


            Mitochondrial Disease is something that is very close to home for me because I myself suffer from it. I may not have hearing loss but could be affected by it sometime in the future. There really isn't enough research to tell me how things will pan out. I do not have one of the disorders listed above but that does not lessen my chance of losing my hearing. I chose to learn about the Deaf Culture not only because I have a huge interest in it, but it also may be my future.

 

References:

 

My Baby's Hearing.Boy Town National Research Hospital. 20 May 2012

http://www.babyhearing.org/hearingamplification/causes/genetics.asp

 

Anonito,Stephanie,"Syndromic Sensorineural Hearing Loss." Medscape. Meyers,Arlene 12 April 2012 http://emedicine.medscape.com/article/856116-overview

 

American Academy of Otolarynogoly-Head and Neck Surgery. 13 October 2011

http://www.entnet.org/HealthInformation/Genes-and-Hearing-Loss.cfm

 

"Hearing Loss in Mitochondrial Disorders." Georgetown University Medical Center. 2005 May.

http://www.ncbi.nlm.nih.gov/pubmed/15965043

 

Causes Of Hearing Loss in Children.American Speech Language Association. 1997-2012

http://www.asha.org/public/hearing/disorders/causes.htm#congenital

 


 


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